Floating boat docks are a very popular means of providing access to boats. In many reservoirs, the water level can vary drastically, changing by as much as 25 ft. In these cases, a fixed boat dock is not practical and a floating boat dock is the only option.
Most floating docks are accessed by means of a bridge or floating walkway. The bridge or floating walkway is typically of a fixed length, say 30 ft. Thus, it is desirable to maintain the floating dock at a fixed distance from the moving shoreline so that the end of the bridge is supported by and accessible from dry land. This requires that the dock move both horizontally and vertically in response to changes in water level. For a reservoir or lake with a bottom grade of 25%, a water level change of 25 ft. would require that the dock move 25 ft. in the vertical direction and 100 ft. in the horizontal direction in order to maintain a constant distance from the shoreline.
Floating boat docks are typically held in place against a shoreline by means of cables and stand-offs. The cables are attached to earth anchors and wound onto take-up winches on the dock. The earth anchors are embedded in the earth above the high water level. The stand-offs are rigid, adjustable legs, typically of structural steel, extending from the dock in the direction of the shore. Cable is taken up onto the winches until the stand-offs are brought into contact with the shore or the bottom of the body of water. In this position, the stand-offs prevent the dock from moving toward the shore and the cables prevent the dock from moving away from the shore. The cables provide tensile elements while the stand-offs provide the balancing compression elements.
This system functions well for maintaining the dock in a constant position relative to the shoreline as long as water level remains constant. When water level changes, however, the dock must be manually adjusted. When water level falls, the stand-offs must be raised, cable must be paid out, the stand-offs must be reset and the cables retensioned. When water level rises, the cables must be taken in until the stand-offs are again in contact with the shore or bottom. Failure to make the adjustments or to make them in a timely manner will result in the floating dock grounding out, i.e. coming to rest on the lake floor, which is damaging to the floatation elements, or developing slack in its mooring cables, which can permit it to swing into other docks, boats or obstacles.
The prior art includes a system for mooring a floating boat dock utilizing cables under constant tension. (U.S. Pat. No. 5,944,451) This system utilizes cables attached to the floor of the body of water beneath the floating dock and taken up or paid out by constant torque reels mounted under the dock. There is no stand-off or any compression element. This system serves to adjust the floating dock vertically in response to changes in water level. Horizontal motion, however, is prevented by the multiple, downward cables. Indeed, it is stated as an objective of the invention to maintain the dock in its original horizontal position.
The prior art also includes a means of addressing the required horizontal motion of a floating dock. (U.S. Pat. No. 5,282,435) This system utilizes a cable anchored both on the shore above the high water level and to the floor of the body of water below the low water level. The portion of the cable extending from the dock into the water can, however, pose a hazard to boaters, swimmers, divers, etc. In addition, the ratchet mechanism included to serve as an adjustable stand-off, which must operate in a hostile environment, may present reliability problems due to parts that must move through a wide range of motion and may become mired in the floor of the body of water.
There is a need for a floating boat dock tethering system that would accommodate both vertical and horizontal motion without manual adjustment of cable tension and stand-off position. It is the object of this invention to provide a means of securing a floating boat dock to the shore of a body of water that will automatically and reliably accommodate both vertical and horizontal motion of the dock to maintain the position of the boat dock relative to the moving shoreline, requiring no intervention of the dock owner or operator, utilizing cable attachments to the shore only.